Treating insoluble indigoid dyes.



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RUDOLF HUTZLER, 0F LUDVTIG$EAEEN 'O1\T THE RHINE, GERMANY, ASSIGNOR -TOBADISCHE AN ILIN 8c SODA FABRIK, OF LUDW'IGSHAEEN-ON-THE-RHINE, GERMANY,

A CORPORATION.

N 0 Drawing.

To all whom it may concern:

Be it known that I, RUDoLF HUTZLER, citizen of the German Empire,residing at Ludwigshafen-on-the-Rhine, Germany, have invented new anduseful Improvements in Treating Insoluble Indigoid Dyes, of which thefollowing is a specification.

The specification of German Patent No. 222,191 describes'a process forbringing in.- soluble coloring, matters into a state of fine division bytreating them, or solutions or sufs pensiqns of their components orleuco compounds, with sulfite cellulose waste liquor, and Example 3 ofthe said specification described a process for blowing air through a hotsolution containing indoxylcarboxylic acid melt and sulfite cellulosewaste liquor and then filtering oil the finely divided indigo I I havenow found'that I can obtain indigoid coloring matters, that is to say,coloring matters of the indigo and thioindigo groups in a colloidal formsoluble in water, that is in such a form that the said coloring mattersdo not settle at all and cannot be separated by filtration from theiralkaline or neutral solutions, including solutions such as are producedaccording to the present invention. In order to secure these results, Ipass air through a cold solution of a leuco compound of one of the saidcoloring matters in the presence of sulfite cellulose waste liquor inthe cold, the reaction being carried out so slowly that only anoxidation to, but not a separation of the coloring matter takes place.

A convenient method of carrying out the process according to thisinvention consists in allowing a thin indigo vat to flow into a solutioncontaining sulfite cellulose waste while well stirring and at the sametime passing air through the solution. The resulting solution or productobtained as aforesaid contains the coloring matter in a state of fin'edivision, such that the coloring matter has no tendency to settle out ofthe solution. This solution can be evaporated or the coloring matter canbe precipitated by means of acid without its capability of dis.- solvingin water being lost.

The following examples will serve to illustrate further the nature of myinvention and how it can be carried into practical effect, but

Specification of Letters Patent.

TREATING INSOIiUBLE INDIGOID DYES.

Patented Mar. 23, 1915.

Application filed September 26, 1913. Serial No. 791,949.

the invention is not confined to these examples.

Example 1: Allow kilos of a- 10% so dium-indigo-white solution(corresponding to 6 kilos of indigotin) to flow at ordinary temperature,while stirring, during a period of 48 hours into 30 liters of sulfitecellulose waste liquor containing about 2,500 grams of cellulose wasteand at the same time pass a slow current of air through the solution.The product obtained can, if desired, be filtered to remove impurities,the indigo remaining in the filtrate. This-filtrate can, after removingsalts, for instance, by means of dialysis, be evaporated; the indigo canthen be precipitated from the solution, for instance, by means of acidwithout its solubility in water being lost. In this example, theindigo-white alkali solution can be replaced by indoxyl alkali solution.

Example 2: Allow 40 kilos of 5% dibromindigo-white sodium solution(prepared from 2 kilos of dibromindigo)fto.,fiow, during 24: hours, into30 liters ofsulfitecellulose waste liquor containing about- 1200 gramsofcellulosewaste, and cause the oxidation to take place in the waydescribed in the foregoing, example. through ealico,uacidify thefiltrate with dilute sulfuric ,acidand then separate the precipitateddyeby means ofa-felt filterg' Wash the coloring matter fora short" ime.with pure water on the filter and then'extract the product during aperiod of se eral days with warm water in an osmoticapparatus forinstance, by placing the suspension as taken from the filter in areceptacle with parchment walls, surrounded by another vessel throughwhich warm water is continuously circulating. The deep blue solutionobtained can be evaporated to dryness, whereupon a blue powder isobtained which willdissolve again in water to a deep blue solution. v

Example 3: Allow 10 kilos of 5% leuco thioindigo solution to flow,during from 4V to 5 hours, into 10 liters of sulfite cellulose wasteliquor containing about 200 grams of cellulose waste, and carry out theoxidation as described in the foregoing Example 1. Acidity the redsolution with dilute sulfuric Filter the product I acid and separate bymeans of a felt filter.

WVash with pure Water until the filtrate begins to assume a red colorand bring the residue into the form of a paste.

Now What I claim is 1. The process of producing indigoid coloringmatters in a colloidal form soluble in water by passing air through acold solution of a leuco compound of one of the said 001- oring mattersin the presence of sulfite cellulose Waste liquor the air being passedso slowly through the solution that an oxidation to the coloring matteris effected, but a separation of the coloring matter is avoided.

2. The process of producing indigo in a colloidal form soluble in waterby passing air through a cold solution of a leuco compound of indigo inthe presence of sulfite cellulose Waste liquor the air being passed soslowly through the solution that an OXldation to indigo is effected, buta separation of the indigo from the solution is avoided.

In testimony whereof I have hereunto set my hand in the presence of'twosubscribing witnesses.

RUDOLF HUTZLER. Wi tnesses I J. ALEo. LLOYD, JOSEPH PFEIFFER.

